Sebastian James, group chief executive of Dixons Carphone – which owns the high street retailer – said in an official announcement: “We take the security of customer data extremely seriously, and we are very sorry that people have been affected by this attack on our systems.

“We are, of course, informing anyone that may have been affected, and have put in place additional security measures.”

Carphone Warehouse is currently contacting all customers affected by the incident. In the meantime, concerned individuals are advised to change their online passwords, monitor account activity and notify their bank or credit card provider.